Silica gel compositions containing alkali metals and alkali metal alloys

ABSTRACT

The invention relates to Group 1 metal/silica gel compositions comprising silica gel and an alkali metal or an alkali metal alloy. The compositions of the inventions are described as Stage 0, I, II, and III materials. These materials differ in their preparation and chemical reactivity. Each successive stage may be prepared directly using the methods described below or from an earlier stage material. Stage 0 materials may, for example, be prepared using liquid alloys of Na and K which are rapidly absorbed by silica gel (porous SiO 2 ) under isothermal conditions, preferably at or just above room temperature, to form loose black powders that retain much of the reducing ability of the parent metals. When the low melting Group 1 metals are absorbed into the silica gel, a mild exothermic reaction produces Stage I material, loose black powders that are indefinitely stable in dry air. Subsequent heating to 400° C. produces Stage II materials, which are also loose black powders. Further heating above 400° C. forms Stage III material with release of some Group 1 metal. It is believed that Stage I, H and III materials represent reductions of the silica gel after absorption of the Group 1 metal. Preferred Group 1 metal/silica gel compositions of the invention are those containing sodium, potassium, or sodium-potassium alloys with sodium and sodium-potassium alloys being most preferred. Each stage of the Group 1 metal/silica gel composition of the invention may be used as a reducing agent reacting with a number of reducible organic materials in the same manner known for alkali metals and their alloys.

RELATED APPLICATION DATA

This application is continuation of U.S. patent application Ser. No.11/692,895, filed Mar. 28, 2007, now U.S. Pat. No. 7,410,567, issuedAug. 12, 2008, which is a divisional of U.S. patent application Ser. No.10/995,327, filed Nov. 24, 2004, now U.S. Pat. No. 7,211,539, issued May1, 2007, which claims benefit of priority of Provisional ApplicationSer. Nos. 60/524,038 filed Nov. 24, 2003, 60/561,886 filed on Apr. 14,2004, 60/578,818 filed on Jun. 14, 2004, 60/611,701 filed on Sep. 22,2004, and 60/611,700 filed on Sep. 22, 2004. The entire disclosures ofeach of the above-referenced applications are incorporated herein byreference.

FIELD OF THE INVENTION

The invention relates to silica gel compositions made by interaction ofalkali metals or alloys of these metals with silica gel. Thecompositions have improved handling characteristics and retain thereactivity of the neutral alkali metal or alloy.

BACKGROUND OF THE INVENTION

Alkali metals, those in Group 1 of the periodic table, and alloys ofalkali metals, are very reactive in their metallic, or neutral, state.The alkali metals and their alloys are very reactive toward air andmoisture and may catch fire spontaneously when exposed to these agents.To avoid the inherent hazards associated with their activity, theneutral metal or alloy must often be stored in vacuo or under an inertliquid such as oil in order to protect it from contact with theatmosphere, which may result in oxidation or other reactions. Forexample, sodium metal is often stored in Nujol oil which must, to avoidunwanted impurities, be removed prior to use in chemical reactions. Thisplaces severe restrictions on its shipment and use.

The combination of alkali metals with silica zeolites, such as ZSM-5,has been extensively studied in many laboratories. For example, it wasrecently shown that pure silica zeolites can absorb up to 12 molepercent cesium from the vapor phase and comparable amounts of the otheralkali metals (except lithium). Prior research with alkali metalencapsulation in all-silica zeolites revealed that such a combinationreacts exothermically with water to produce hydrogen quantitatively.(See, for example, “Toward Inorganic Electrides”, A. S. Ichimura, J. L.Dye, M. A. Camblor and L. A. Villaescusa, J. Am. Chem. Soc., 124,1170-1171 (2002) and “Inorganic Electrides Formed by Alkali MetalAddition to Pure Silica Zeolites”, D. P. Wernette, A. S. Ichimura, S. A.Urbin and J. L. Dye, Chem. Mater. 15, 1441-1448, (2003). Theconcentration of sodium absorbed by the zeolite compositions, however,was too low to be practical. In addition, the reaction was relativelyslow with slow sodium diffusion within the limited zeolite pore size.

The use of potassium metal dispersed on silica as a reagent in organicsynthesis has been reported by Levy et al., Angew. Chem. Int. Ed. Engl.20 (1981) p. 1033. Potassium metal was dispersed onto silica gel (CASRegistry No. 7631-86-9: actually colloidal silica, which has no internalsurface area) producing an amorphous material. The reactivity of thematerial was demonstrated with water and benzophenone, as shown below.See also, Russel, et al., Organometallics 2002, 21, 4113-4128, Scheme 3.

A need exists, therefore, to have alkali metals and their alloysavailable in a form that may be easily handled without a significantloss in metal reactivity. This invention answers that need.

SUMMARY OF THE INVENTION

The invention relates to a Group 1 metal/silica gel compositioncomprising the product of mixing a liquid Group 1 metal with silica gelin an inert atmosphere under isothermal conditions sufficient to absorbthe liquid Group 1 metal into the silica gel pores. The Group 1metal/silica gel composition produced reacts with dry O₂. This materialis referred to as “Stage 0” material.

The invention also relates to a Group 1 metal/silica gel compositioncomprising the product of mixing a liquid Group 1 metal with silica gelunder exothermic conditions sufficient to absorb the liquid Group 1metal into the silica gel pores. The Group 1 metal/silica gelcomposition produced does not react with dry O₂. This material isreferred to as “Stage I” material.

In addition, the invention relates to a Group 1 metal/silica gelcomposition comprising the product of mixing a liquid Group 1 metal withsilica gel under conditions sufficient to absorb the liquid Group 1metal into the silica gel pores and heating the resulting mixture to atemperature of between about 215° C. to about 400° C. The Group 1metal/silica gel composition produced does not react with dry O₂. Thismaterial is referred to as “Stage II” material.

The invention also relates to a Group 1 metal/silica gel compositioncomprising the product of mixing a liquid Group 1 metal with silica gelunder conditions sufficient to absorb the liquid Group 1 metal into thesilica gel pores and heating the resulting mixture to a temperature ofabove about 400° C. The Group 1 metal/silica gel composition produceddoes not react with dry O₂. This material is referred to as “Stage III”material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a Differential Scanning Calorimetry (DSC) diagram showingtraces of a 1:1 NaK/silica gel sample (8.9 mg).

FIG. 2 is a Differential Scanning Calorimetry (DSC) diagram showingtraces of a 1:1 Na₃K/silica gel sample (5.7 mg).

FIG. 3 is a Differential Scanning Calorimetry (DSC) diagram showingtraces of a 1:1 cesium/silica gel sample (6.7 mg).

FIG. 4 shows the conversion of silica gel particles coated with an alloyof composition Na₂K to the loose, shiny, black Stage I powder.

FIG. 5 is a Differential Scanning Calorimetry (DSC) diagram showingtraces of 2.4 mg Na mixed with 3.9 mg of silica gel.

FIG. 6 shows the inflation of a balloon with hydrogen after adding waterto style II sodium/silica gel material.

FIG. 7 is Differential Scanning Calorimetry (DSC) diagram showing theresults of heating Stage 0 material overnight at about 140° C. in vacuoor in an inert atmosphere.

FIG. 8 shows an optical spectrum of an anthracene radical anion obtainedby the reduction of anthracene with the Stage I material of theinvention.

FIG. 9 shows a ¹H NMR spectrum of the product of a Birch Reduction ofanthracene in THF by passage through a mixed bed column of the Group 1metal/silica gel composition of the invention.

FIGS. 10A-10C show the results of an analysis of the product ofreduction of benzyl chloride in a batch process.

FIGS. 11A-11C show the results of an analysis of the product of anovernight batch reaction of phenyl sulfide with the Stage I material ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

Group 1 Metals: Alkali Metals and Alkali Metal Alloys

Alkali metals are those metals in the Group 1 family of the periodictable. The terms “Group 1 metal” or “Group 1 metals” are used here todescribe alkali metals and alloys of alkali metals which may be used inthe silica gel compositions of the invention. Those alkali metalsinclude sodium (Na), potassium (K), rubidium (Rb), and cesium, (Cs). Ofthese alkali metals, sodium and potassium are preferred for use in thesilica gel compositions of the invention, with sodium being particularlypreferred.

Alkali metal alloys may also be used in the silica gel compositions ofthe invention. The alkali metal alloy is preferably an alloy of two ormore alkali metals, for example sodium-potassium (NaK) alloys, which areparticularly preferred. Other preferred alkali metal alloys are thosecontaining, potassium, cesium, and rubidium with each other andparticularly alloys of these elements with sodium. The alkali metalalloys are within the “Group 1 metal” definition as used in thespecification and claims.

In preparing the Group 1 metal/silica gel compositions of the invention,the Group 1 metal is typically mixed with the silica gel. The viscosityof the liquid Group 1 metal should be at least low enough to be absorbedby the silica gel. One method to accomplish this is heating the alkalimetal in an inert atmosphere prior to mixing it with the silica gel.Alternatively, depending on the stage of material to be prepared, theGroup 1 metal may be mixed as a solid with the silica gel and themixture heated to melt the alkali metal.

Another method to introduce Group 1 metals into silica gel is from thevapor phase as was done with zeolites. (See A. S. Ichimura, J. L. Dye,M. A. Camblor and L. A. Villaescusa, J. Am. Chem. Soc., 124, 1170-1171(2002) and D. P. Wernette, A. S. Ichimura, S. A. Urbin and J. L. Dye,Chem. Mater. 15, 1441-1448, (2003).) In another method, a Group 1 metalcan be deposited onto the silica gel from a metal-ammonia solution. (SeeM. Makesya and K. Grala, Syn. Lett. 1997, pp. 267-268, “ConvenientPreparation of ‘High Surface Sodium’ in Liquid Ammonia: Use in AcyloinReaction.”) The metal-ammonia solution can be used to avoidagglomeration of the metal in upon mixing with the silica gel and toprepare an intimate mixture of the metal with the silica gel. However,in practice the metal-ammonia solution method of mixing Group 1 metalswith silica gel was accompanied by considerable decomposition of themetal-ammonia solution to form amides. However, as preferred for theinvention, simply allowing the liquid Group 1 metal to contact thesilica gel avoids the time-consuming vapor deposition or metal-ammoniaroutes.

As discussed below, for at least Stage 0 material, it is generallypreferred that the Group 1 metal have a melting point within about 15°C. of room temperature (25° C.). For example cesium and rubidium havemelting points of 28.5° C. and 38.5° C., respectively. Typically alloysof the two or more alkali metals are, and preferably are, liquid at ornear room temperature. A preferred low-melting alloy is that betweensodium and potassium (NaK) at various molar ratios of Na to K between0.5 and 3.0 more preferably with a 2:1 molar ratio, Na₂K. All Na—Kalloys with mole ratios between 0.5 and 2.5 begin melting eutecticmelting temperature of −12.6° C. Melting is complete at 25° C. for moleratios of about 0.12 and 3.1. Other binary alloys of the alkali metals,such as Cs with Rb, K, or Na and Rb with Na or K also melt below, oronly slightly above room temperature and would therefore be appropriateto use for this purpose. Ternary alloys, made from three of these fouralkali metals, or an alloy of all four would also melt at low enoughtemperatures to form a Group 1 metal/silica gel composition of theinvention.

Silica Gel

Silica gel is a porous form of amorphous silica. It is a free-flowingpowder that is listed as 99+ percent SiO₂. Silica gel is readilyavailable and inexpensive. Silica gel generally has a pore volumeranging from about 0.6 to about 1.2 cm³/g, and a surface area rangingfrom about 300 to about 750 m²/g. Silica gel is commonly available inthe following mesh sizes: 3-8, 6-16, 14-20, 14-42, 30-60, 28-200, and assmall as mesh 325. Given its porous nature, silica gel can take up largeamounts of absorbed material. The silica gels used in the silica gelcompositions of the invention preferably have pore sizes ranging from 50Å to 1000 Å. Preferably, the pore size may range from 100 to 300 Å. Morepreferably, the average diameter of the pores of the silica gel will beapproximately 150 Å. Preferred forms of silica gel include Davisil™Grades 646 and 50, which are both 30 to 60 mesh obtained from chemicalsuppliers such as Aldrich and directly from the Davison ChemicalDivision of WR Grace Company, (i.e., 150 Å pore size, granular, 30-60mesh, plain white, no indicator). An alternate supplier of such silicagel is the Eagle Chemical Division of Multisorb.

Although silica gel, when purchased, is a free-flowing powder, ittypically contains large amounts of gaseous material, such as water andair. These are preferably removed prior to mixing the silica gel with analkali metal or alloy to form compositions of the invention. The silicagel may be degassed using methods known in the art. For example, toremove the gaseous material the silica gel may be heated under vacuum inan evacuable flask, first with a hot air dryer and then with a torch.Such heating achieves temperatures of approximately 300° C. It is alsopossible, and is actually preferred, to remove the gases more easily andto passivate active sites by heating the silica gel to 600° C. or hotter(900° C.) in air (calcination). It is believed that heating the silicagel to 600° C. or higher causes at least some of Si—OH sites in thepores or silica gel lattice to form siloxane, Si—O—Si, groups with theconcomitant loss of water. Heating the silica gel at a lower temperaturewould also produce a usable starting material, but a portion of thealkali metal would probably be rendered inert by reaction with defectSi—OH groups. The silica gel is typically cooled to room temperaturebefore preparing a Group 1 metal/silica gel composition of theinvention.

Silica Gel Compositions Containing Alkali Metal and Alkali Metal Alloys

The ability to utilize alkali metals or their equivalents in aconvenient form continues to be a need in the chemical industry and forthe hydrogen production community. Answering that need, the inventionrelates to Group 1 metal/silica gel compositions comprising silica geland an alkali metal or an alkali metal alloy. The compositions of theinventions are described as Stage 0, I, II, and III materials. Thesematerials differ in their preparation and chemical reactivity. Eachsuccessive stage may be prepared directly using the methods describedbelow or from an earlier stage material. Stage 0 materials may, forexample, be prepared using liquid alloys of Na and K which are rapidlyabsorbed by silica gel (porous SiO₂) under isothermal conditions,preferably at or just above room temperature, to form loose blackpowders that retain much of the reducing ability of the parent metals.It is believed the Stage 0 materials have small clusters of neutralGroup 1 metal absorbed in the silica gel pores. The Stage 0 materialsare pyrophoric but less explosive in air as compared to their parentGroup 1 metal. Stage 1 materials may be prepared by heating Stage 0materials at 140° C. overnight. Stage I material is a loose black powderthat are indefinitely stable in dry air. Subsequent heating to 400° C.produces Stage II materials, which are also loose black powders. Furtherheating above 400° C. forms Stage III material with release of someGroup 1 metal. It is believed that Stage I, II and III materialsrepresent reductions of the silica gel after absorption of the Group Imetal. Preferred Group 1 metal/silica gel compositions of the inventionare those containing sodium, potassium, or sodium-potassium alloys withsodium and sodium-potassium alloys being most preferred.

As described below, a number of samples of this material with NaK andcesium, at various loads and mass ratios, were tested by DifferentialScanning Calorimetry (DSC). The heat absorbed upon melting NaK in thesilica gel pores at −25-0° C. was used to determine the amount ofencapsulated metal that remained as metal in the silica gel. This wasfollowed by broad exothermic peaks between 5° C. and 650° C. Uponcooling and reheating the same sample, no appreciable thermal peaks wereobserved. This shows that the heat treatment causes encapsulated metalin the pores to react with silica gel to produce Stage II and then StageIII material, although the boundaries are not sharp. This conversion toStage II and III material does not appreciably change the hydrogenproducing abilities of the material.

The Group 1 metal/silica gel compositions of the invention comprisesilica gel with absorbed Group 1 metal. The amount of Group 1 metalloading is dependent upon the pore size and pore density of the actualsilica gel used. Typically, the Group 1 metal may be present in thecompositions of the invention up to about 50% by weight. Preferably, theamount of metal ranges from 30% to 40% by weight. In the Stage I, II,and III materials of the invention, loadings above about 40% by weightresult in some free metal remaining in the silica gel pores.

The Group 1 metal/silica gel compositions of the invention react rapidlywith water to produce gaseous hydrogen in near quantitative yield,typically about 95% yield. The Group 1 metal/silica gel compositions ofthe invention, whose preparation and properties are described below,show promise as easily shipped and handled sources of clean hydrogen andas powerful reducing agents for a variety of reactions of organiccompounds. Table I below summarizes the preparation processes and usesof Stage 0, I, II, and III materials.

TABLE I Summary of Stages 0, I, II, and III Material Preferred Metals/Type Alloys Used Preparation Procedures Stage 0 Liquid alloys (NaK,Na₂K, Under inert atmosphere or vacuum, liquid etc.) alkali metal alloyis added to silica gel at or near room temperature. On a large-scale,this process would be best done by adding the liquid metal or alloy tosilica gel spread in a metal pan that would dissipate any heat which maybe produced. Stage I Liquid alloys (NaK, Na₂K, Under inert atmosphere orvacuum, liquid etc.) or vapor alkali metal is added to silica gelCesium, Rubidium, etc. and is agitated for several minutes to hours at atemperature below 150° C. Stage II Sodium Under inert atmosphere orvacuum, alkali Potassium metal or alloy is added to silica gel and isNa-K alloys heated to between 215° C.-400° C. to incorporate all metaland to reduce sensitivity to air. Stage III Sodium Under inertatmosphere or vacuum, alkali Potassium metal or alloy is added to silicagel and is Na-K alloys heated to 215° C. to incorporate all metal, andthen gradually heated above 400° C. over several hours which makes aSi-rich silicide in the silica gel.

As discussed above, to prepare all of the Group 1 metal/silica gelcompositions of the invention, it is preferred to degas and passivatethe silica gel prior to mixing it with the Group 1 metal. Typically, inpreparing the materials of the invention, the silica gel is initiallyheated to approximately 600° C. or higher in air to remove water, de-gasthe silica gel, and minimize defect sites. Other methods known in theart to dry, de-gas and/or passivate the silica gel may also be used.

Stage 0 Material

The Stage 0 material of the invention apparently contains low-meltingGroup 1 metals absorbed into the pores of silica gel without reaction ormetal redistribution into the silica gel lattice. Thus, it can be viewedas nanoscale alkali metal or alkali metal alloy particles in the openpores and channels absorbed within the silica gel. The Stage 0 materialof the invention is a Group 1 metal/silica gel composition comprisingthe product of mixing a liquid Group 1 metal or a liquid Group 1 metalalloy, such as Na₂K, with silica gel under isothermal conditionssufficient to absorb the liquid Group 1 metal or liquid Group 1 metalalloy into the silica gel pores. Preferred Group 1 metals for Stage 0materials include a low-melting Group 1 metal such as cesium or a NaKalloy. The Stage 0 Group 1 metal/silica gel composition reacts with dryO₂, which differentiates it from Stage I, II, and III materials. SinceStage 0 material is reactive with dry air, it should be handled invacuo, in an oxygen-free atmosphere, and preferably in an inertatmosphere, such as under nitrogen or an inert gas. While the Stage 0material will ignite spontaneously in air, it can be stored under suchconditions in a closed container, e.g. a screw-top vial.

To form Stage 0 materials, a Group 1 metal is mixed with silica gel inan inert atmosphere under isothermal conditions, preferably at roomtemperature or slightly above, for a time sufficient to permit thealkali metal or alloy to be absorbed into the silica. The mixing must bedone in an inert atmosphere such as within a glove box or glove bag.During formation of a preferred Stage 0 material, a liquid Group 1metal, such as Na₂K, may be poured over a bed of silica gel at roomtemperature. The mixture is agitated, preferably stirred or shaken, toachieve good mixing. The liquid Group 1 metal is preferably absorbedinto the porous silica gel without any significant heat of reaction orappreciable release of heat.

Depending upon the Group 1 metal used, the absorption of the liquidGroup 1 metal to form Stage 0 material preferably occurs within 15° C.of room temperature (25° C.). In the typical process, so little heat isevolved that the sample does not become noticeably warm but converts toa product which is a free-flowing amorphous black powder, in which theindividual particles have a shiny surface. The mixture is agitated for atime sufficient to allow the alkali metal or alloy to be absorbed or“soaked up” by the silica gel. The time of mixing generally depends uponthe batch size of material being prepared and may range from severalminutes to several hours. (This mixing time holds true for thepreparation of any Group 1 metal/silica gel composition of theinvention.)

When preparing Stage 0 material, any heat generated by the reaction orput into the reaction should be controlled or dissipated. A significanttemperature increase during the preparation should be avoided. In apreferred embodiment the Stage 0 material is formed near roomtemperature (25° C.). Heating much above this temperature generallyleads to the formation of Stage I material. The temperature may becontrolled by spreading the silica gel (for example, on a metal tray),stirring the silica gel, or by cooling the reaction vessel. The reactiontemperature should, however, be maintained such that the Group 1 metalremains liquid so that it may be absorbed by the silica gel. It shouldalso be noted that Stage 0 material can slowly convert to Stage Imaterial over time when kept at room temperature, although furtherconversion to Stage II material does not occur without heating asdiscussed below.

The Stage 0 material is a shiny black powder that reacts exothermicallywith water. A DSC of the Stage 0 material shows the presence of thealkali metal in its neutral state within the silica gel. While the exactcomposition of the Stage 0 material is not currently known, the meltingpoint of the Stage 0 material is lower than the melting point of themost common Group 1 alloys, such as NaK, thus indicating that smallparticles of the Group 1 alloys are within the pores of the silica gel.

FIG. 4 illustrates the absorption of Na₂K alloy into silica gel at roomtemperature to form a loose, shiny, black Stage 0 powder. As shown inFIG. 4, the flask shown in (A) contains silica gel coated with Na₂Kalloy immediately after mixing. The flask shown in (B) contains thefinal loose black material after shaking the sample in flask (A) for afew minutes. It is an apparently homogeneous, easily poured blackpowder.

The Stage 0 materials are the most reactive members of the Group 1metal/silica gel compositions of the invention. Since the addition of alow-melting alkali metal or alloy to silica gel produces a Stage 0material without significant heat evolution, the Stage 0 materialretains most of the reducing ability of the alkali metal. Because oftheir reactivity toward air and moisture they must be handled with careand not allowed to come in contact with large amounts of air andmoisture. In spite of these restrictions, the Stage 0 materials haveutility in highly reducing chromatography applications. The porosity ofpacked columns of the Group 1 metal/silica gel compositions of theinvention provide a reducing environment that cannot be met with theparent metals or alloys. This, as discussed below, permits the Stage 0material to be used to produce hydrogen from water and as a reducingagent reacting with a number of reducible organic materials in a mannersimilar to that of the pure alkali metals.

Stage I Material

The Stage I material of the invention is a Group 1 metal/silica gelcomposition comprising the product of mixing a liquid Group 1 metal withsilica gel under exothermic conditions sufficient to absorb the liquidGroup 1 metal into the silica gel pores. The Stage I Group 1metal/silica gel composition produced does not react with dry O₂. In theStage I material it appears that the alkali metal or alloy has beenconverted to a form that loses the properties of the bulk metal, such asmelting. The framework within which the active reducing material isdispersed appears to be largely SiO₂. Pair Distribution Functionexperiments on the Stage I material exhibit predominantly silicon andoxygen peaks with no crystallinity which suggests that the alkalimetal(s) have ionized to form alkali cations, with the electronsreleased to the silica framework or to the void spaces. See Billinge, etal., Chem. Commun. 2004, pp. 749-760 for a discussion of PairDistribution Function.

The Stage I material of the invention may be formed by mixing the liquidGroup 1 metal, at or just above its melting point with silica gel underan inert atmosphere to allow the Group 1 metal to be absorbed into thepores of the silica gel. The Group 1 metal may also be mixed with thesilica gel using one of the alternative methods discussed above, such asadding the Group 1 metal as a vapor. The mixture is then maintained ator slightly above the melting point of the Group 1 metal (i.e.,approximately 70° C. to 150° C.) and agitated for between severalminutes to several hours. Generally speaking, higher reactiontemperatures convert the material in shorter times. The reaction to formStage I materials is mildly exothermic, and, on a large scale, theprocess would be preferably done by adding the liquid metal or alloy tothe silica gel in a metal pan that would remove heat as it is produced.The reaction appears to form an alkali metal-silica gel lattice. Theexothermic nature of the reaction differentiates Stage I material fromStage 0 material. Heating above the exotherm can convert Stage Imaterial to Stage II or Stage III material, depending upon thetemperature.

When low-melting Group 1 metals are added to calcined and outgassed SGin a closed environment such as an Erlenmeyer flask, the system oftenbecomes warm because of exothermic reactions between the alkali metaland the silica gel or its defect sites. This can result in the formationof mixtures of Stages 0 and I. The simplest and most direct preparationof Stage I materials is to heat Stage 0 samples overnight under an inertatmosphere at temperatures of 140° C. Other times and temperatures maywork also, but care should be taken to avoid overheating, which can leadto the formation of Stage II. To insure a homogeneous product, provisionshould be made for agitation during the heating process.

The Stage I material is an amorphous, shiny black powder that does notimmediately react with dry air, but reacts exothermically with water. ADSC of the Stage I material shows little or no Group 1 metal remainingwithin the silica gel. The difference between Stages I and 0 is that theformer can be handled in dry air and even quickly transferred inordinary laboratory air without catching fire or degrading rapidly. Whenkept under an atmosphere of dry oxygen for hours to days, Stage Imaterial (in contrast to Stage 0 material which reacts which dry O₂) isunchanged and produces the same amount of hydrogen gas upon reactionwith liquid water as do fresh samples.

Stage I material has many uses in reactive chemistry as an activereducing agent, and is a better reducing agent than the Stage IImaterial described below. It is probably the reagent of choice for bothbulk and chromatographic reductions.

Stage II Material

Stage II material of the invention is a Group 1 metal/silica gelcomposition comprising the product of mixing a liquid Group 1 metal withsilica gel under exothermic conditions sufficient to absorb the liquidGroup 1 metal or liquid Group 1 metal alloy into the silica gel poresand heating the resulting mixture to a temperature of between about 215°C. to about 400° C. For example, melting sodium in a mixture of sodiumand silica gel and heating in a closed vessel at 400° C. overnightcauses complete inclusion of sodium in the silica gel pores and forms aStage II sodium/silica gel composition. Preliminary Pair DistributionFunction experiment on sodium Stage II material show the presence ofnanocrystalline sodium silicides (a compound of stoichiometry NaSi, e.g.Na₄Si₄) in the silica gel composition. There appears to be no sodiummetal present.

In the course of heating to between about 215° C. to about 400° C., anexothermic reaction begins and the Stage II material is formed. Stage Imaterial can then be converted to Stage II material. All of the Group 1metal is incorporated into the silica gel and the air sensitivity of theresulting material is reduced. Higher melting Group 1 metals, e.g.sodium and potassium, typically do not wet the silica gel attemperatures which lead to formation of Stage 0 or Stage I materials.Sodium, potassium and other high melting Group 1 metals then form StageII materials. The reaction appears to form an alkali metal—silica gellattice, such as sodium silicide in the example mentioned above. Thestability and reactivity of Stage II material, produced by heating StageI samples, is similar to that of the material formed by heating highermelting alkali metals such as sodium or potassium with silica gel.

As discussed, Stage II materials can be made from either Stage 0 orStage I materials by heating them in an inert atmosphere slowly orstepwise to 400° C. For the higher melting alkali metals Na and K, themetal can be heated above its melting point in the presence of calcined,outgassed silica gel and then slowly heated to 400° C. with occasionalshaking. In a typical heating procedure, the material in a sealed PyrexErlenmeyer flask was heated for 1-3 hours each at 150, 200, 250 and 300°C., followed by overnight heating at 400° C. After each heating periodthe flask was vigorously shaken to prevent undue “clumping”. The productis a loose black powder that pours easily when the preparation remainshomogeneous. If the heating is too rapid or the molten metal is notmixed with the silica gel vigorously, the product can contain lumps thatmust be manually crushed.

The Differential Scanning Calorimetry (DSC) traces of pure Na plus SGare shown in FIG. 5. FIG. 5 illustrates DSC traces for 2.4 mg Na+3.9 mgSG. The overall (exothermic) heat of reaction is about −90±10 kJ/moleNa. Note that the endothermic heat of melting of Na (113 J/g Na), whichappears in the initial trace (510) at 98° C., is absent in the repeattrace (520), as are the exothermic peaks. This shows that Na reactedwith silica gel during the first run, probably to form the silicide,NaSi. The Stage II reaction of sodium with silica gel releases about 90kJ of heat per mole of sodium. The melting endotherm of Na metal,present in the initial trace at 98° C., is absent in the subsequent run,showing that the metal has reacted with the silica gel. The reactionproducts have not been positively identified, but Na plus SG probablyforms sodium silicide (of overall composition NaSi) in the 15 nmdiameter pores of the silica gel used, with concomitant formation ofsodium silicate. X-ray powder patterns indicate that the product isstill amorphous.

The Stage II material is an amorphous, matted black powder. The Stage IIGroup 1 metal/silica gel composition produced does not react with dryO₂or with dry air. Stage II material is easily handled in environmentscontaining dry air. The loose black powders of Stage II material areeasily handled in an open ambient environment and do not change withtime when kept in the presence of low humidity, such as in a closedcontainer. In fact, the Stage II material is the least reactive of theGroup 1 metal/silica gel compositions of the invention. However, thismaterial still reacts rapidly with water to yield almost quantitativeamounts of pure hydrogen gas.

FIG. 6 shows the inflation of a balloon with hydrogen after adding waterto a sample of a Stage II sodium/silica gel composition of theinvention. The Stage II composition was approximately 30-40% metal byweight. As is shown in image (A), prior to the addition of water, theballoon contains a dry powder under vacuum. Image (B) shows the balloontwo minutes after addition of water. The reduced silica gel plus wateris still bubbling at this stage. One gram of the powder produces about170 cm³ of H₂ at p=1 atm and 25° C. This material is a convenient,portable source of clean hydrogen upon demand, with the only gaseousproducts being hydrogen and water vapor.

Although it is the least reactive of the Group 1 metal/silica gelcompositions of the invention, the Stage II material has many uses inreactive chemistry, as a passive reducing agent, and for hydrogenproduction. Stage II material can degrade slowly by picking up moisturefrom the air, but does not catch fire and can be easily transferred inordinary laboratory air. The reducing ability does not appear to be asstrong as the other stages, but it may be useful in many reductions thatdo not require the full reducing power of alkali metals. For example,Stage II material can reduce anthracene to dihydroanthracene in thepresence of a proton source, but the reduction is slower than with StageI materials. Because of its insensitivity to ambient air, Stage IImaterial is a preferred reagent for the production of hydrogen byreaction with water.

Stage III Material

Stage III material of the invention is a Group 1 metal/silica gelcomposition comprising the product of mixing a liquid Group 1 metal withsilica gel under exothermic conditions sufficient to absorb the liquidGroup 1 metal into the silica gel pores and heating the resultingmixture to a temperature of above about 400° C., and preferably aboveabout 500° C. The Stage III Group 1 metal/silica gel compositionproduced does not react with dry O₂.

As with the preparation of the other Group 1 metal/silica gelcompositions of the invention, to prepare Stage III material, the Group1 metal is mixed with the silica gel under an inert atmosphere orvacuum. In a preferred method, the mixture is first heated toapproximately 215° C.-400° C., (forming Stage II material) and thenslowly heated to approximately 400° C.-600° C. over several hours. Asthe temperature is increased above 400° C., a sharp exotherm occurs. Thereaction appears to form an alkali metal-silica gel product thatcontains a silicon rich silicide. The Stage III material is anamorphous, matted black powder that does not react with dry air. If thereaction is to be carried to Stages II or III by heating, the exothermicnature of the reaction would indicate that any large-scale preparationswould need a provision for heat removal in order to prevent a “runaway”thermal reaction. In addition, heating can release alkali metal vapor ifmixing is not efficient. Thus, as would be appreciated by those skilledin the art, a closed system is likely required for large scaleproductions.

The Stage III material may have many uses in reactive chemistry, as adoping material, and for hydrogen production.

As discussed above, the various stages of the Group 1 metal/silica gelcompositions of the invention may be prepared in sequence for eachsuccessive stage. For example, adding a 1:1 mole ratio of sodium andpotassium (liquid) to silica gel at 25° C. results in the formation of afree-flowing black powder, a Stage 0 material. In this case, subsequentheating in a closed vessel at 400° C. overnight caused further reactionto produce a less reducing powder, Stage II material. Further heatingabove 400° C. causes further reaction and produces Stage III material.The Differential Scanning Calorimetry (DSC) traces shown in FIG. 1indicate that the exothermic reaction of NaK with silica gel occurs inat least two steps. In FIG. 1, a Differential Scanning Calorimetry (DSC)shows traces of a 1:1 NaK/silica gel sample (8.9 mg), wherein the toptrace (110) is for a fresh room temperature sample and the bottom trace(120 ) is a repeat run after cooling the sample. The inset (130) is anenlargement of the low temperature region of the first trace showing amelting endotherm that corresponds to about 50% of the added metal. Thetotal value of ΔH for the exothermic processes corresponds to between−100 and −125 kilojoules per mole of metal.

FIG. 2 shows similar behavior for a Group 1 metal/silica gel compositionprepared with Na₃K and an equal mass of silica gel. In FIG. 2, a DSCdiagram shows traces of a 1:1 Na₃K/silica gel sample (5.7 mg), whereinthe top trace (210) is for a fresh room temperature sample and thebottom trace (220) is a repeat run after cooling the sample. The inset(230) is an enlargement of the low temperature region of the first traceshowing a melting endotherm that corresponds to only about 10% of theadded metal. The total value of ΔH for the exothermic processescorresponds to between −75 and −100 kilojoules per mole of metal. Stage0 is produced at or near room temperature without significant heatproduction. Stage II forms spontaneously upon heating to 215-400° C.,and Stage III is the final product obtained by heating at to 400-600° C.

Reaction Chemistry of the Group 1 Metal/Silica Gel Compositions

All Group 1 metal/silica gel compositions of the invention react withwater exothermically to produce hydrogen in essentially quantitativeyield based on the Group 1 metal. Thus, advantageously, the compositionsof the invention retain the reactivity of the Group 1 metal. Stage 0material can be handled briefly in dry air, but it reacts slowly withoxygen and rapidly with moisture. By contrast, Stages I, II and III ofthe Group 1 metal/silica gel compositions are completely unreactivetowards dry oxygen.

Although the Stage I, II, and III Group 1 metal/silica gel compositionsof the invention are relatively innocuous and not violently reactive,they do have a strong base present and forms alkali metal hydroxidesupon reaction with water. When the metal content is high (about 35% orabove) the reaction product with water is completely soluble, probablyas the basic metal silicate. Neutralization with acid precipitatessilica.

Each stage of the Group 1 metal/silica gel composition of the inventionmay be used as a reducing agent reacting with a number of reducibleorganic materials in the same manner known for alkali metals and theiralloys. For example, the Group 1 metal/silica gel compositions may beused to reduce aromatic compounds to their radical anions as is commonin the so-called Birch reductions, commonly carried out with alkalimetal—ammonia solutions. A Birch reduction is a general method ofreduction of aromatic compounds by alkali metals in liquid ammonia. Thetheoretical and preparative aspects of the Birch reduction have beendiscussed in several reviews. See, G. W. Watt, Chem. Rev., 46, 317(1950); A. J. Birch, Quart. Rev. (London), 4, 69 (1950); A. J. Birch andH. F. Smith, Quart. Rev. (London), 12, 17 (1958); and C. D. Gutsche andH. H. Peter, Org. Syntheses, Coll. Vol. 4, 887 (1963). The Group 1metal/silica gel compositions of the invention can be readilysubstituted for the sodium in Birch reductions. Example 10 shows a Birchreduction using a Group 1 metal/silica gel composition of the invention.

Similarly, violent reductions such as the Wurtz reduction of halogenatedorganic compounds such as PCB's might be carried out under controlledconditions. The Wurtz reaction is the coupling of two organic radicals(R) by treating two moles of the organic halides (RX) with two moles ofsodium:2RX+2Na→R—R+2NaXSee A. Wurtz, Ann. Chim. Phys. [3] 44, 275 (1855); Ann. 96, 364 (1855).;J. L. Wardell, Comp. Organometal. Chem. 1, 52 (1982); W. E. Lindsell,ibid. 193; B. J. Wakefield, ibid. 7, 45; D. C. Billington, Comp. Org.Syn. 3, 413-423 (1991). The Group 1 metal/silica gel compositions of theinvention can be readily substituted for the sodium in a Wurtz reactionor other such dehalogentation reaction. Compositions of the inventionhave also been used to dehalogenate inorganic halides. Example 11 showsa Wurtz reduction using a Group 1 metal/silica gel composition of theinvention.

Industrially useful reactions as desulfurization of petroleum might becarried out with Group 1 metal/silica gel compositions of the invention.As an example, the compositions of the invention may be used in animproved method of removing sulfur from phenyl sulfide to producebiphenyl. The improvement comprises carrying out the following reaction:

where M-SG is a Group 1 metal/silica gel composition of the invention.

Use of the Group 1 metal/silica gel compositions of the invention allowalkali metal reactions such as those described above to be carried outunder safer conditions due to the safer handling of the compositionsover the corresponding alkali metal or alloy. Use of the compositionsalso generally gives higher yields than the corresponding reaction withjust the Group 1 metal.

Because Stage I material (such as a Stage I Na₂K/silica gel composition)is very easy to prepare and retains much of the reducing ability of theparent Group 1 metal, it is likely to find use as a powerful andconvenient reducing agent. Small glass columns filled with the Stage Ipowder are able to reduce a variety of organic compounds when they aredissolved in tetrahydrofuran (THF) and passed through the column.Alternatively, batch reactions can be carried out simply by stirring THFsolutions of the organic compounds with the Stage I material. Forexample, as is shown below, benzophenone (1) is reduced to the radicalanion (ketyl); benzyl chloride (2) undergoes Wurtz reduction to formbibenzyl (3), and dibenzothiophene (4) is reduced to the radical anionand ultimately to a mixture of products that are free of the startingmaterial. Other reactions include the Wurtz reduction of dichlorobenzeneto form the expected coupling products and the Birch Reduction ofanthracene to dihydroanthracene.

Stage II sodium/silica gel composition, as noted above, is easier tohandle in air than Stage I material. Its production of hydrogen byreaction with water is quantitative and it is also able to carry outmany of the organic reductions described above for the Stage I material.For example, it can reduce benzophenone (1) to the radical anion and itcan convert benzyl chloride (2) to bibenzyl (3). Numerous otherreactions of Stage I and II materials are possible and likely. Thereduction of the representative compounds discussed above indicate thatthe Group 1 metal/silica gel compositions of the invention can reducearomatic compounds to the radical anions or dianions, breakcarbon-sulfur bonds, and completely dechlorinate aromatic chlorides.This material might therefore be able to destroy PCB's by dechlorinationand carry out desulfurization reactions. The powerful reducingproperties of the Group 1 metal/silica gel compositions also permit theuse of chromatographic columns packed with this material for thereduction of organic and inorganic compounds that are now reduced byNa—K or alkali metal-ammonia solutions.

A major use for all four stages of reduced silica gel compositions ofthe invention is in the fuel storage potential and the formation ofhydrogen gas needed for mobile fuel cells. For example, large stocks ofthe reduced silica gel powder might be kept on conveyor trays within aholding tank. Addition to water would liberate pure hydrogen gas pluswater vapor. All stages produce near quantitative amounts of thehydrogen that would have been produced from the alkali metal used. Thehydrogen could then be used to power mobile fuel cells. For example,stocks of the Group 1 metal/silica gel compositions might be kept onconveyer trays within a holding tank. Water is then introduced and themixing with the water would liberate hydrogen which can then beextracted and compressed or pressurized. The compressed hydrogen wouldbe used to fill mobile fuel cells. The spent powder, at this stage isnow just silica gel or dissolved metal silicate that could bereactivated with new Group 1 metal or used for other purposes.

Another embodiment of the invention relates to the use of silica gel toclean up Group 1 metal spills and similar remains from spent operations.This embodiment takes advantage of the absorptive nature of the silicagel discussed above in the preparation of the compositions of theinvention. As described in example 8, upon performing experiments withcesium metal in the glove box, several grams of the cesium was spilledonto the box floor. Kimwipe tissues were first used to clean up thespill, but the dirty wipes would ignite once removed from the heliumfilled glove box. It was then decided to try and absorb the cesium usingsilica gel hoping to make it stable enough to make it from the box to asafe place for disposal before ignition in air. This lead to the use ofsilica gel to clean up metal or other spills, in particular reactivemetals such as alkali metals, where the metal was a liquid or could bemelted to form a liquid. When dealing with high melting alkalis, themetals must be heated to a liquid state for cleanup to occur.

Compositions using alkali metals, e.g. sodium, potassium, etc., deliveractive substances, e.g. to vaporize fragrances in deodorizercompositions, are described in U.S. patent application Ser. 10/248,765,“System for Delivery of Active Substances”, which is incorporated hereinby reference. Due to their stability the Stage I, II and IIIcompositions of the invention and compatible with such activeingredients, e.g. fragrances. In yet another embodiment, the inventionalso relates to a such compositions containing Group 1 metal/silica gelcompositions of the invention. For example, the deodorizer compositionmay contain about 5 to 15 weight percent of a reduced silica gel of theinvention, 10 to 30 weight percent of a fragrance, and up to about 75weight percent of a neutralizer and/or organic acid. In addition to thefragrance, a deodorizer may also contain other active ingredients suchas disinfectants, surfactants, and colors or dyes. The reaction of theGroup 1 metal/silica gel composition with water distributes thefragrance or other active ingredient.

EXAMPLES Example 1

An exemplary silica gel, Davisil 30 to 50 mesh, was obtained fromGrace-Davison as a free-flowing powder that is listed as 99+ percentSiO₂. However, it contains large amounts of gaseous material, probablywater and air. In order to remove the gaseous material the silica gelwas heated under vacuum in an evacuable Erlenmeyer flask, first with ahot air dryer and then with a torch. The estimated temperature reachedapproximately 300° C. As discussed above, silica gel can be out-gassedmore easily (with passivation of active sites) by heating the materialto 600° C. or hotter in air (calcination).

Example 2

One significant feature of the Group 1 metal/silica gel compositions ofthe invention is their ability to produce pure hydrogen gasquantitatively upon addition to water. The “reducing power” of the Group1 metal/silica gel compositions was determined by adding water to anevacuated sample and collecting hydrogen with a modified Toeppler pump.The reducing power is defined as the weight percent of alkali metal oralloy used that would produce the same amount of hydrogen. This wasverified by collecting the hydrogen produced from a known mass ofmaterial upon reaction with out-gassed water. The hydrogen was collectedin a calibrated pipette using a modified Toeppler pump (mercury filled).The amount of hydrogen produced was generally equivalent to the amountthat would have been produced by the metal(s) alone. Such analyses wererun on every sample of reduced silica, regardless of the stage of thematerial. For example, if a 40 wt % sample of NaK in Stage I silica gelproduced the same amount of hydrogen as would be produced by that amountof NaK alone, the reducing power would be 40%. The total amount ofalkali metal hydroxide formed was then determined by the addition of HCland back-titration with sodium hydroxide. The difference between thetotal alkali metal percentage as obtained from the titration and thereducing power is presumably a measure of the concentration of SiOHgroups and other sources of hydrogen. Alkali metals can react with suchgroups during sample preparation to release hydrogen. This reaction ispresumably the origin of the detectable amounts of gas formed during themixing of the metal or alloy with the silica gel.

Example 3

Using a stainless steel pan inside of a helium filled glove box, 14 g ofoutgassed and calcined silica gel was mixed with 9.7 g of Na₂K from aPasteur pipette to create Stage 0 material. The Na₂K was added drop wiseto various regions of the silica gel coated pan. The drops of alloy wetthe silica gel and could be “squashed” with a spatula to aid the alloyinclusion. The product never got warm and appeared to have a very shinysurface indicating free metal on the surface. It appeared that the Na₂Kwas not completely absorbed into the silica gel pores. The sample wasthen setup for Differential Scanning Calorimetery (DSC) by putting 3.6mg of the sample into a DSC pan. The DSC was run from ˜−55 to 60° C.,held for ten minutes, and then re-run. After, the sample was run to 450°C. twice. The endotherm of melting corresponded to ˜135 J/g metal, whichis slightly higher than expected based on metal added. The weighed masscould be off or we could have inhomogeneities in concentration. Whenheated to 60° C. and held for ten minutes and then repeated gave aΔH_(melt)=61.4 J/g metal showing an annealing effect is already presentto convert to sample to the next stage. The “reducing power” of thesample was determined by adding water to an evacuated sample andcollecting hydrogen in a modified Toeppler pump. The reducing power isdefined as the amount of Group 1 metal that would be required to producethe same amount of hydrogen. A H₂ evolution from 21 mg of the samesample yielded 37% reducing power. This is in agreement with the nominal40 wt % metal concentration.

Example 4

The conversion of Stage 0 material to Stage I material can be performedby both aging the sample or by uniform heating. Simply heating Stage 0material overnight at about 140° C. in vacuo or in an inert atmospherewhile mixing converted it to the Stage I form that shows little or nomelting endotherm by DSC (See FIG. 7). Because of the small particlesize, Stage 0 material starts to melt at −25° C. rather than at the bulkonset temperature of −13° C. The small value of ΔH (9 J/g metal) forStage I material compared with 117 J/g metal for Stage 0 shows that mostof the metal is probably converted to alkali metal cations. The apparentabsence of free alkali metal in the pores or on the surface of thesilica gel particles makes this stage totally free of oxidation in dryair.

Example 5

The preparation of Stage II material can be performed by continuousheating of Stage 0 and Stage I materials to 400° C. or by using thehigher melting alkali metals, such as sodium and potassium. Outgassedand calcined silica gel 13.5 g, was weighted out and about 7.3 g of Nametal was added. The silica gel was outgassed with heating to a pressureof 3.5×10⁻⁵ torr. The combination of silica gel and Na was heated firstto 150° C. for 1 hr, then shaken vigorously, then heated to 200° C. for1.5 hrs. The material was shaken vigorously approximately every 30minutes. Lastly, the material was heated to 300° C. overnight. Thepowder looked loose and free flowing. The temperature was then raised to400° C. and the material was heated 3 more hours.

Example 6

In preparation for NaK inclusion into silica gel, 3.00 g of 600° C.calcined silica gel was placed in an Erlenmeyer flask with 3.012 g ofNaK. The NaK alloy was made with 5.562 g of Na and 9.433 g of K. Thismass of NaK has about 50 mmol each of Na and K and 50 mmol of SiO₂.Therefore, a 2:1 mole ratio of metal to Si was used in the sample. Atroom temperature, the silica gel began to turn black and went to auniform, pourable shiny black powder within several minutes without anynoticeable exothermicity. From the sample, 22.6 mg were removed for H₂analysis. The H₂ evolution was performed at T=296.6 K and P_(atm)=738.9Torr. After evolution, there was 176.5 μmol H₂ corresponding to 353 μmolof metal. This H₂ evolution corresponds to 48.4 wt % of metal in thesilica gel, nominally the 50 wt % initial loading. The sample can thenbe heated through a controlled process to achieve Stage I and IImaterial. It should be noted, however, that heating the flask duringpreparation can initiate a strongly exothermic reaction causing themetal to “bump” and coat the vessel.

Example 7

A number of different preparations with varying amounts of metal+silicagel were prepared that had alkali metal concentrations of 20 to 50weight %. One sample was prepared with Na and silica gel loaded to a45.6% reducing power. The reducing power was generally 94% or more ofthe maximum that could be obtained based on the amount of metal added.The remaining 2-6% represented reaction of the alkali metal(s) withdefect sites. The measurement of the reducing power after varioustreatments such as exposure to oxygen or heating was used to provideinformation about the stability of this material. In 48 hrs, thereducing power decreased to only 44%, a total loss of 1.6%, indicatingalmost no reaction with oxygen in the absence of moisture. It ispossible to use other alloys with different ratios of Na to K that are aliquid at or near room temperature. For example, we have prepared areduced silica using Na₃K with results similar to that described inExample 5. The sample was prepared by adding 8412 mg of silica gel to433 mg of Na₃K in an Erlenmeyer flask in a helium-filled glove box. Twoother samples with a 1:1 mass ratio of NaK to silica gel have also beenprepared. Lastly, a sample was prepared with a 1:4 mass ratio of NaK tosilica gel. All of these samples formed Stage I free-flowing blackpowders that are stable in dry air. Long term storage in the glove boxresulted in no detectable change in properties.

Example 8

We had a liquid Cs spill within the helium glove box. This led us todiscover an effective clean-up process for alkali metals. Silica gel waspoured upon the Cs spill and was mixed around with a Kimwipe. All of theCs metal was absorbed into the silica gel turning the silica gel a blackcolor. Thus, silica gel makes an ideal clean-up material for low meltingalkali metals and eutectic alloys, such as NaK.

Example 9

The behavior of pure cesium was similar to that of NaK alloy, as shownin FIG. 3. In FIG. 3, a DSC diagram shows traces of a 1:1 cesium/silicagel sample (6.7 mg), wherein the top trace (310) is for a fresh roomtemperature sample and the bottom trace (320) is a repeat run aftercooling the sample. The total value of ΔH for the exothermic processescorresponds to about −120 kJ/mol metal. Note the absence of a meltingexotherm of Cs metal. But, since 50 wt % Cs contains less than 0.5 molesCs/mol silica, no melting endotherm of Cs metal was observed in the DSCexperiments. Four samples of cesium-loaded silica gel have beenprepared; two were prepared by vapor-phase addition and one by thedirect addition of cesium metal to the silica gel. All threepreparations formed free-flowing powders. The two vapor-phase additionswere prepared at room temperature and 40° C., respectively. Lightloadings of cesium, <20 wt %, by vapor-phase addition formed reducedsilica that was blue in color. Higher concentrations yieldedfree-flowing black powders. Heating Stage I material formed Stage IIand/or Stage III reduced Cs-containing silica gel with the evolution ofheat. For example, FIG. 3 shows the DSC result of heating 1:1 Stage ICs-silica gel to 650° C. and then reheating the cooled sample. It can beseen that the first heating resulted in an exothermic reaction that wasnot present in the reheated sample. This shows the conversion of Stage Imaterial to Stage III and the absence of further significant reaction ofthe Stage III material.

Example 10

All of the alkali metal-silica gel powders, from Stage 0 to Stage II,are able to reduce anthracene to the radical anion by Birch reduction.The reduction was observed by the formation of an intense blue color ofthe solution and verified by obtaining the optical absorption spectrumof the product (See FIG. 8). FIG. 8 shows an optical spectrum of ananthracene radical anion obtained by the reduction of anthracene withthe Stage I material of the invention, M-SG. This is essentially thesame as the known spectrum of this anion. This radical anion is stableenough to persist in solution for many hours. This reaction can beperformed using several reaction setups, such as a batch reaction, alayered (alkali metal-silica gel layered on top of commercial silicagel) chromatographic column, and a mixed (alkali metal-silica geluniformly mixed with commercial silica gel) chromatographic column,typically 50:50 ratio of materials. Either the layered- or the mixed-bedchromatography column could be used with the alkali metal-silica gel toreduce anthracene and protonate the resulting radical anion with itsretained water. The product is 9,10 dihydroanthracene as expected. Thereaction may be illustrated as is shown below.

FIG. 9 shows a ¹H NMR spectrum of the product of a Birch Reduction ofanthracene in THF by passage through a mixed bed column of the Group 1metal/silica gel composition of the invention. The yield in this caseusing Stage I material was 92% of the desired product and the totalelution time was less than two minutes. Further experimentation resultedin a 100% yield. This illustrates the efficiency of the Birch reductionfor a reactant that readily forms a radical anion. The GC-MS analysis ofa bulk reaction product that had been protonated with t-butanol showedprimarily only anthracene and 9,10 dihydroanthracene. It should be notedthat column chromatography with Stage II material instead of Stage Imaterial yielded less product, indicating that reduction is slower withthis less reactive reduced silica gel. The data in Figures for thereaction with a Stage I Na₂K/silica gel material, (˜30-40 wt % Na₂K).

Example 11

One of the earliest reactions of alkali metals with organic compounds isthe Wurtz reaction in which de-halogenation of a chlorocarbon results incoupling to form a new carbon-carbon bond. When used with a bulk alkalimetal and the neat chlorocarbon however, the reaction can be dangerouslyexplosive. As is shown below, this coupling reaction was carried outwith ˜130 mg of benzyl chloride dissolved in 10 ml of THF by reductionwith ˜1.3 g of Stage I Na₂K/silica gel material (˜30-40 wt % Na₂K).Partial reduction (˜30%) occurred upon rapid passage through the smallcolumn. However, further experimentation resulted in a complete, 100%yield when using Stage I and Stage 0 Na₂K/silica gel materials (˜30-40wt % Na₂K) upon rapid passage through the column. Therefore, speed ofcolumn pass through will vary the extent of reactant conversion todesired product. Bulk reduction had occurred after 3 hours of stirringwith the Stage I Na₂K/silica gel material. The only product detected byboth GC-MS and ¹H NMR was bibenzyl (See FIGS. 10A-10C). FIGS. 10A-10Cshow the results of an analysis of the product of reduction of benzylchloride in a batch process. FIG. 10A shows a single line GC trace, FIG.10B shows a mass spectrum of GC product, and FIG. 10C shows a ¹H NMR ofthe product. The MS shown in FIG. 10B matches exactly the MS ofbibenzyl. Note the complete absence of the peak for the reactant benzylchloride at 4.6 ppm.

Other dehalogenation include the dechlorination of 1,2 dichlorobenzene(partial through the column, complete in bulk). These tests show thatboth aromatic and aliphatic halocarbons can be readily de-halogenated bythe Group 1 metal/silica gel composition of the invention.

Example 12

Sulfur elimination from hydrocarbon sulfides can present many problemsand yield a myriad of products. It was rather surprising, therefore,that the batch reaction of phenyl sulfide with Stage I Na₂K/silica gel(˜30-40 wt % Na₂K) yielded only biphenyl as a product, as shown below.This was verified by both GC-MS and ¹H NMR (See FIGS. 11-11C). FIGS.11A-11C show the results of an analysis of the product of an overnightbatch reaction of phenyl sulfide with the Stage I material of theinvention. FIG. 11A shows a single peak GC trace, FIG. 11B shows a massspectrum of GC product, and FIG. 11C shows a ¹H NMR of the product. TheNMR in FIG. 11C is primarily the NMR spectrum of biphenyl. It also showsthe presence of chloroform from the deuteron-chloroform used as well assome phenyl sulfide reactant. The yield cannot be qualified because ofNMR overlap in the region of chemical shift at around 7.3 ppm, but theproduct is mostly biphenyl. Similarly, sulfur was completely removedfrom dibenzothiophene, a process that is particularly difficult inhydrocarbon desulfurization. Again GC-MS showed the primary product tobe biphenyl, although ¹H NMR showed the presence of other products.

Example 13

An important initial question for the use of the Group 1 metal/silicagel compositions of the invention was whether metallic Group 1 metalsare present in the reduced silica composition. To test this, a sample offinely divided sodium and silica gel was prepared. Since the sodiumtends to agglomerate easily, it was prepared by evaporating ammonia froma frozen solution of sodium in ammonia. Three portions of this materialwere tested by differential scanning calorimetry (DSC). The heatabsorbed upon melting sodium at 98° C. was used to determine the amountof sodium in the sample. This was followed by broad exothermic peaksbetween 100° C. and 490° C. There was also a sharp endothermic peak ofunknown origin at 280° C. Upon cooling the sample and reheating, nothermal peaks were observed. This shows that heat treatment completelyremoves free sodium, presumably because of reaction of sodium with thesilica. Moreover, solid state Na NMR showed no metallic sodium presentin the reduced silica gel composition. Additionally, it was possible toestimate the heat of reaction of the product “reduced silica” withwater. The heat of reaction (exothermic) of the reduced silica withwater is approximately −136±18 kJ/mol Na, which is about 75% of that ofpure sodium. Thus, the Group 1 metal/silica gel compositions of theinvention release considerable heat when it reacts with water.

The total amount of sodium hydroxide formed was then determined by theaddition of HCl and back-titration with sodium hydroxide. The differencebetween this result and the reducing power is presumably a measure ofthe concentration of SiOH groups. The Group 1 metal can react with suchgroups during the preparation to release hydrogen. This reaction ispresumably the origin of the large amount of gas formed during themelting of sodium in the presence of silica gel.

Example 14 Preparation of a 50 wt % Sodium-Potassium Reduced Silica Gel

First, about 40 g of silica gel was heated in air overnight at 600° C.to out-gas the silica gel. 3.0 g of this silica gel was furtherout-gassed with heating to about 300° C. under high vacuum (2×10⁻⁵ torr)in an adapted long-neck Erlenmeyer flask. Next, the flask was placed ina helium-filled glove box via an evacuated port. Then 3.0 g NaK (1:1molar ratio) was added to the flask that contained the silica gel toform a 50:50 mass ratio of silica gel to NaK. At this point the NaKbegan to wet the silica gel surface turning the silica gel black. Afterremoval from the glove box, the flask was evacuated to approximately2×10⁻⁵ Torr. A small amount of agitation provided enough activation forthe entire sample to be converted to a free-flowing black powder (StageI). Upon the reaction, there was no detectable heat release. A secondsample, warmed with a heat gun, spontaneously reacted exothermicallysuch that the flask became too hot to touch. Presumably, this convertedthe Stage I material to another form (Stage II or Stage III).

Example 15 Preparation of Sodium-Containing Reduced Silica Gel

First, 2.25 g of silica gel was heated under vacuum to outgas the silicagel. The flask was then removed from the heat after no more gas evolvedand the pressure reached 3×10⁻⁵ Torr. Next, the flask was then placed ina glove box filled with helium via an evacuated port. After being placedin the glove box, 1.135 g Na was added to the flask. Liquid ammonia(NH₃) was then freeze-pumped once and distilled over the Na-silica gelpowder, thereby causing the following catalyst decomposition reaction:Na+NH₃→NaNH₂+½H₂

The line was then incrementally pumped out because of the significantamount of H₂ which evolved during the catalyst decomposition reaction.Any remaining NH₃ was then removed and the flask was evacuated to 3×10⁻⁵Torr. Next, the flask was heated with a heat gun under vacuumconditions. After heating, the flask was placed back in the glove box.The sample was then distributed into 5 vials. The first vial (449 mg)was removed from the glove box and was stored at room temperature. Thesecond, third, and fourth vials (509 mg, 603 mg, and 653 mg,respectively) were placed in the glove box freezer. The fifth sample(122 mg) was placed in a sealed vial before being dumped into a 1000 mLbeaker of water.

Example 16 Preparation of Sodium-Containing Reduced Silica Gel

First, 2.2786 g of 99⁺% silica gel (30-50 mesh) was added to anErlenmeyer flask. The flask was then heated and out gassed under vacuumconditions, first with a heat gun, then with a torch. The torch fuel(O₂) was adjusted to give a yellow tip to the torch flame. After heatingand out gassing the silica gel, approximately 2.145 g of silica gelremained with a volume of 2.5 cm³. The flask was then heated and pumpedto a pressure of 2×10⁻⁵ Torr. After being heated, 980 mg of Na wasrolled into cylinders and added to the flask. The target amount of Nawas 1.0 g. As the Na melted in the flask, the pressure changed toapproximately 10⁻³ Torr. The flask was heated intermittently for 90minutes under vacuum as more gases evolved. The flask was then cooled toroom temperature and sealed off at 2×10-5 Torr. Next, the flask washeated until any Na remaining on the walls of the flask was distilledonto the surface of the silica gel. Finally, the flask was then placedin a furnace at 210° C. overnight. The sample was then distributed into4 vials. All four vials (812 mg, 771 mg, 823 mg, and 525 mg plus anyremainders, respectively) were placed in the freezer.

Example 17 Fragrance Testing

Two samples of Na/silica gel mixture from Example 2 above were obtainedfrom freezer. The first sample weighed 520 mg. 684 mg of Citrus Oilfragrance was freeze pumped 3 times to a pressure of 2×10⁻⁵ Torr andplaced in a He filled glove box. The first sample of Na/silica gelmixture was then added to the Citrus Oil in the glove box. The samplewas then evacuated with liquid N₂ cooling. The sample was then allowedto warm to room temperature and the gases produced by the reaction ofthe Na/silica gel and the Citrus Oil were measured. The sample was thenheld at room temperature for 110 minutes to observe reaction. The samplewas then cooled with liquid nitrogen and water was allowed to condenseonto the sample for 5 minutes. The sample was then allowed to warm topermit reaction of the sample with water. All gases were then collectedand measured.

The second sample weighed 109.7 mg. 161 mg of Citrus Oil fragrance wasfreeze pumped 3 times to a pressure of 2×10⁻⁵ Torr and placed in a Hefilled glove box. The second sample of Na/silica gel mixture was thenadded to the Citrus Oil in the glove box. The sample was then evacuatedwith liquid N₂ cooling. The sample was then allowed to warm to roomtemperature and the gases produced by the reaction of the Na/silica geland the Citrus Oil were measured. The sample was then held at roomtemperature for 110 minutes to observe reaction. The sample was thencooled with liquid nitrogen and water was allowed to condense onto thesample for 5 minutes. The sample was then allowed to warm to permitreaction of the sample with water. All gases were then collected andmeasured.

Example 18 Deodorizer Compositions

A first deodorizer composition containing 0.8 g citric acid, 0.35 gsodium bicarbonate, 0.11 g sodium containing reduced silica gel, and0.27 g fragrance. A second deodorizer composition containing 0.8 gcitric acid, 0.35 g sodium bicarbonate, 0.11 g sodium containing reducedsilica gel, and 0.35 g fragrance. A third deodorizer compositioncontaining 0.8 g citric acid, 0.35 g sodium bicarbonate, 0.11 g sodiumcontaining reduced silica gel, and 0.5 g fragrance.

1. A Group 1 metal/silica gel composition having a Group 1 metalabsorbed into the silica gel pores, wherein the Group 1 metal/silica gelcomposition reacts with dry O₂.
 2. The Group 1 metal/silica gelcomposition of claim 1 wherein the pores of said silica gel have anaverage pore size of approximately 50 to 1,000 Å.
 3. The Group 1metal/silica gel composition of claim 1 wherein the pores of said silicagel have an average pore size of approximately 150 Å.
 4. The Group 1metal/silica gel composition of claim 1 wherein the Group 1 metal isselected from the group consisting of rubidium, cesium, and an alloy oftwo or more Group 1 metals thereof.
 5. The Group 1 metal/silica gelcomposition of claim 4 wherein the Group 1 metal is a sodium-potassiumalloy.
 6. The Group 1 metal/silica gel composition of claim 1 whereinthe Group 1 metal is present in an amount up to 50% by weight.
 7. AGroup 1 metal/silica gel composition having a Group 1 metal or Group 1metal alloy absorbed into the silica gel pores, wherein the Group 1metal/silica gel composition produced does not react with dry O₂.
 8. TheGroup 1 metal/silica gel composition of claim 7 wherein the pores ofsaid porous silica gel have an average pore size of approximately 50 to1,000 Å.
 9. The Group 1 metal/silica gel composition of claim 7 whereinthe pores of said porous silica gel have an average pore size ofapproximately 150 Å.
 10. The Group 1 metal/silica gel composition ofclaim 7 wherein the Group 1 metal is selected from the group consistingof rubidium, cesium, an alloy of two or more Group 1 metals thereof. 11.The Group 1 metal/silica gel composition of claim 10 wherein the Group 1metal is a sodium-potassium alloy.
 12. The Group 1 metal/silica gelcomposition of claim 7 wherein the Group 1 metal is present in an amountup to 50% by weight.
 13. The Group 1 metal/silica gel composition ofclaim 12 wherein the loading of the Group 1 metal is present in anamount of 30-40% by weight.